We didn't focus on individual contributions, only on community-level metrics. The reputation metric we used rewards frequency of contributions (questions, answer, comments) and that turned out to make a difference in building a strong core.

Also, core is not static, sustainable communities have the ability to "pull" new users into the core, so new, enthusiastic users are not discarded by the existing core.

If you are interested in individual efforts and user archetypes take a look at another work: https://arxiv.org/abs/1709.05111